The main function of modern rail clips is to hold the rail down so firmly that the rail will not become longer when the sun heats the rail & then not become shorter when the rail is subject to colder & freezing conditions. In other words the rail must compress or stretch but not move in the tie rail seats.
Long lengths of welded rail are commonly used so the longitudinal forces in the rail due to temperature change are very high. This means that the rail clips must clamp the rail very tightly.
A popular rail clip is described in U.S. Pat. No. 431,563 (Young).
Sometimes the clips become damaged & lose some of their clamping force which allows the rail to “run” in the tie rail seats. This can then cause serious problems to occur in the track which in the worst case can end in a derailment & train smash.
The main cause of clip damage is the clip fitting machines being out of adjustment and overdriving the clips during track maintenance.
This often happens in tight track curves where the high lateral forces on the rail cause the pads & insulators to wear so the clips have to be frequently removed for renewing these parts. This frequent removal & refitting of the clips increases the chance of an out of adjustment fitting machine damaging the clips.
In some cases the clips are routinely replaced in locations where they must be frequently removed. This is a considerable expense which should not be necessary since with many clip designs the clips have an indefinitely long fatigue life and do not “wear out”. The replacement need is solely caused by clip fitting machine damage.
It is an object of this invention to provide a rail clip having a much reduced likelihood of losing a significant part of the toe load & thereby increasing the track safety & eliminating the need to replace damaged clips.